- From: David Booth <david@dbooth.org>
- Date: Wed, 12 May 2010 21:56:41 -0400
- To: Dan Connolly <connolly@w3.org>
- Cc: Pat Hayes <phayes@ihmc.us>, Jonathan Rees <jar@creativecommons.org>, AWWSW TF <public-awwsw@w3.org>
On Wed, 2010-05-12 at 10:31 -0500, Dan Connolly wrote: [ . . . ] > "Other things, such as cars and dogs (and, if you've printed this document on physical > sheets of paper, the artifact that you are holding in your hand), are resources too. > They are not information resources." > > so w:InformationResource is disjoint with cars, dogs, and pieces of paper. > > That suggests fairly strongly that it's disjoint with people, but doesn't > say so exactly. How about Graphs? Integers? I don't find any compelling > argument based solely on ratified specs and/or decisions of the TAG. It is pointless to make claims about what is or isn't disjoint with w:InformationResource when we do not have either a formal definition -- a set of assertions -- of w:InformationResource or of "dog", "person", etc. If we make up RDF definitions of those terms *then* we can talk about what is disjoint and what isn't. Furthermore, as I've pointed out before, there is no architectural *need* to define w:InformationResource as disjoint with something like sumo:Person (from the SUMO upper ontology). Ambiguity of resource identity is inescapable -- we just have to accept that fact and learn to deal with it -- so although the AWWW (correctly, in my view) admonishes people to mint different URIs for different things, http://www.w3.org/TR/webarch/#URI-collision the choice of what to consider *different* (versus what to benignly conflate) will always be an application-dependent judgement call that seeks to balance immediate simplicity against support for other -- more discerning -- uses of the URI(s). A single URI for X may be perfectly adequate and unambiguous for one application, while a different application may need to distinguish between X1 and X2, which were conflated by using a single URI for X. There is no significant benefit to the web architecture by trying to insist that w:InformationResource must be distinct from some notion of person. The salient architectural advice was already given the AWWW section on avoiding URI collisions: http://www.w3.org/TR/webarch/#URI-collision Given that advice, it is up to URI owners to decide where to draw the line between simplicity and support for other uses of a URI. (Incidentally, this does not mean that the notion of "information resource" is useless: it is an important role in the web architecture. An "information resource" is the kind of thing that can have "representations".) I know of no other reasonable and general way to define the identity of a resource than by specifying a set of assertions that constrain it. And of course, in the semantic web world, the natural way to do that is with a set of RDF assertions. Given that it would be (IMO) completely nonsensical for different people to arbitrarily assume completely different resource definitions for a given URI, the next logical question is: how should the resource identity for a URI be determined? Or another way to state this is: how should the resource identity for a URI at least be *minimally* constrained, given that it will be further constrained in different applications. This leads to the notion of a URI declaration. http://dbooth.org/2007/uri-decl/ One can think of a URI declaration as providing a set of constraints that (minimally) limit the possible interpretations for that URI that are permissible. Of course, when a URI is used in a semantic web application there will normally be *additional* assertions involving that URI, and those will additionally constrain the potential interpretations for that URI, just as illustrated in step 3a of figure 3: http://dbooth.org/2009/denotation/ Thus, it is perfectly reasonable that one URI owner may mint a URI that denotes something that is both an w:InformationResource and an RDF graph, while another URI owner chooses to distinguish between them by minting separate URIs. Again, without a definition of the resource identity for each URI (e.g., a URI declaration for each) there is no basis for deciding whether they are disjoint or not. -- David Booth, Ph.D. Cleveland Clinic (contractor) Opinions expressed herein are those of the author and do not necessarily reflect those of Cleveland Clinic.
Received on Thursday, 13 May 2010 01:57:09 UTC